This invention relates generally to emissive displays including organic light emitting device (OLED) displays, light emitting diode (LED) displays and electro luminescence (EL) displays.
Emissive displays generally include a cover glass or transparent sheet over the light emissive elements. The transparent sheet generally is substantially transparent to light emissions. The thinner the glass sheet, normally the less its optical effects.
In displays made by combining a plurality of tiles, each including a cover glass, gaps may exist between adjacent tiles. The thicker the glass that is utilized, the more apparent are these gaps to viewers of such displays.
While the use of thin cover glasses has many advantages, it also has concomitant cost disadvantages. Thinner glass generally breaks more easily. In addition, manufacturing equipment is designed for certain minimum glass thicknesses. Using thinner glass may result in cost penalties or require the development of specialized equipment for handling glass processing.
Thus, the thicker the cover glass that is utilized, the more apparent are any gaps between adjacent tiles. The composite image of a large area display is the result of the images contributed by each of the tiles making up the large area display. To the extent that the individual tiles may be delineated because of the inter-tile gaps, the overall seamless effect of the display is lessened. Therefore, it is desirable to produce large area displays in which the individual tiles making up the displays are as invisible and undiscernible as possible.
Thus, while using thicker glass has many practical advantages, it may also increase the likelihood that seams between adjacent tiles become visible. Therefore, there is a need for a way to make the gaps between adjacent tiles less visible in large area displays.
State of the art tile displays, such as video walls, use mullions between individual tiles to hide the physical gap. However, if these mullions are discernible to the user, they are objectionable because they break the continuity of the image.
Another structure commonly found in non-tiled displays is a pattern of black lines. The black lines, like a mullion, produce inter-pixel black lines. A black line is put between the pixels to absorb ambient light in those areas in order to increase the display contrast. Black lines are found in non-modular displays such as cathode ray tubes and liquid crystal displays. With these displays, the black lines are smaller than the mullions. They are placed in the plane of the pixels, located between the pixels. Because the pattern of black lines is periodic and placed between pixels, it does not break the continuity of the image.
Thus, there is a need for ways to make the seams of large area displays less visible.